Device for mixing apparatus

ABSTRACT

The invention relates to a mixing device for use in mixing apparatus, the device comprising a rotor having a plurality of blades secured to its surface and received within a stator which has a plurality of grooves on its inner wall. Guide faces and depressions are provided on the rotor to provide preferential guide paths for the material being mixed. The rotor may be in the form of an inverted truncated cone or a slightly tapering cylinder, the stator being funnel-shaped or in the form of a hollow cylinder respectively. The mixing apparatus may be used for mixing various materials including pigments and resins in printing ink and paint manufacture and the dispersion of rubbers and resins in the manufacture of adhesive compositions.

[4 1 Jan.21, 1975 DEVICE FOR MIXING APPARATUS [75] Inventor:

Sidney Henry Wright, London, England Primary ExaminerPeter Feldman Assistant Examiner-Alan Cantor [73] Assignee: Winn & Coales (Denso) Ltd., Attorney Agent, or & Thomas London, England Feb. 6, 1973 57 ABSTRACT The invention relates to a mixing device for use in [22] Filed:

21 Appl. No.: 330,010

mixing apparatus, the device comprising a rotor hav- [30] Foreign Application Priority Data ing a plurality of blades secured to its surface and re- Feb. 10, 1972 Great Britain.........'.............

ceived within a stator which has a plurality of grooves. on its inner wall. Guide faces and depressions are pro- [52] U S Cl 259/107 259/7 241/257 R vided on the rotor to provide preferential guide paths for the material being mixed.

24l/26l.1 BOli 7/16, B07f 7/24, B02c 13/28 The rotor may be in the form of an inverted truncated 259/7, 8, 23, 24, 43, 44, cone or a slightly tapering cylinder, the stator being 259/66, 67, 96, 107, 108, DIG. 30; 241/277,

h c .r a e S m .m e MF 1] 18 55 funnel-shaped or in the form of a hollow cylinder respectively.

S S w mw l b too 6 anwh 1' rd f .mw X f. n S 1 0 S m flfi .W flpm F 6. dc n 8 0 a .I u e W u G in 8 0. 8 m ynnm aea 6 mm 1 we e 8.1 h S w w m 39 .1 Ina hm alf dU 1 C pu 0 3 S mm 1 m Fmm mbna mm m mflp mddm h nno Tmaac 6 76 9 W9 9/59 5925 25 .2 .2 m" T. m m N m w W m m MA t a. .I C t. .u S S e Ed in CT 6W nA n e W FT c zm SCSGP D E96 6 4566 1999 9 1111 N//// 23 5 0000 2364 7 9 9 3 899 m M364 5 4 7 9 2 .l. 2223 Patented Jan. 21, 1975 8 sheets-sheet 1' Pafented Jan. 21, 1975 8 Sheets-Sheet 2 Patented Jan. 21, 1975 8 Sheets-Sheet 5 Patented Jan. 21, 1975 8 Sheets-Sheet 4 Patented Jan. 21, 1975 3,861,655

8 Sheets-Sheet 5 Patented Jan. 21, 1975 8 Sheets-Sheet 6 Patented Jan 21, 1975 8 Sheets-Sheet 7 Patentd Jan. 21, 1975 8 Sheets-Sheet 8 DEVICE FOR MIXING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to mixing mechanisms and in particular to a device suitable for use in vertical shaft mixers.

2. DESCRIPTION OF THE PRIOR ART Mixers which have been used for disintegrating solids in the presence of liquids or solvents, or for dispensing solids in liquids generally comprise a rotor or pump head of cylindrical form having two or more vanes protruding outwardly, the outer faces of the vanes being semicicular. The rotor is generally contained within a stator of tubular form and the faces of the rotor vanes are in close proximity to the stator inner wall which is usually perforated by a series of holes or slots, subsequently referred to herein as apertures.

A variation of the stator form is with a cap or plate at one end and in this form the cap is perforated, not the wall. The rotor vanes are in close proximity to both the wall and the inner face of the cap. The rotor is mounted on a shaft which is rotated by a prime mover.

A vertical cylindrical container for the materials to be processed in some instances forms a part of the machine, or removable containers are used. The rotor stator mechanism described above is situated inside the container.

In operation the materials, i.e. liquids or liquids and solids are drawn into the stator and expelled centrifugally through the apertures by the rotor (with a capped stator the centrifugal motion is transformed into an ascending or descending spiral motion according to which end of the stator is capped).

Considering firstly the apparatus as a disintegrator, in which solids are reduced in particle size in the presence of liquids, particle size reductions are achieved by the actions of the leading edges of the rotor vanes as they approach and pass the trailing edges of the stator apertures, the edges acting in the manner of guillotines in solids trapped between them. The trapping and shearing action is the useful, or critical phase of the motion of the rotor, during the remainder of the motion the stator apertures are either obscured by rotor vanes or they allow materials to flow freely through them without shearing. As the useful phase of the motion is determined by the particle size of the solids the apparatus becomes less efficient as the particles are reduced in size. In this mechanism when solids are sheared approximately 50% is immediately expelled through the stator apertures; the balance remains within the stator until expelled during the open phase or re-sheared during the critical phase. The apparatus used as a disintegrator is therefore inefficient; when the apparatus is used for emulsification or dispersion, useful work is only performed when the stator apertures are nearly obscured by the rotor vanes and the liquids, or liquids and solids are forced through the gaps by pressure developed by the rotor vanes. While the stator apertures are open the apparatus functions merely as a stirrer.

SUMMARY OF THE INVENTION According to the present invention there is provided a mixing device for use in mixing apparatus said device comprising a rotor and a stator, said rotor being rotatable about its longitudinal axis and having at least one blade secured thereto, said blade being substantially axially disposed along the rotor and radially extending from the rotor,

said rotor having a guideface adjacent said blade, said guide face being spaced from the working edge of the blade in a radially inward direction, for guiding the flow of the materials to be mixed in close proximity to the blade towards the cutting edge of the blade such that, when the rotor is rotated, the guide face is upstream of the blade,

said rotor further having a depression disposed substantially axially along the rotor adjacent the guide face,

at least part of said rotor bearing said blade being located within said stator and being substantially coaxial therewith,

said stator having an inner wall which has a plurality of grooves, the width of the grooves being greater than the thickness of the blades.

In one embodiment the rotor takes the form of an inverted truncated cone and is located within a stator having a generally funnel-shaped configuration. In another embodiment the rotor is of generally cylindrical shape, the stator being in the form of a hollow cylinder in order to accommodate the rotor.

The rotor preferably has a plurality of blades secured to its surface and each of these may follow a helical path around the rotor. Between adjacent blades there may be a depression which may also follow a helical path around the rotor. On one or each side of the blades a guide face is provided or the clamp by which the blade is secured to the rotor may function as a guide face. The widths of the blades and guide faces may be uniform along their length or they may be tapered at one or both of their sides respectively. These features that is the blades, guide faces and depressions, when positioned helically on the rotor can in many cases provide two different flow rates for the materials being mixed, disintegrated or emulsified and passing between the rotor and stator. The two different flow rates may be achieved by reversing the direction of rotation of the rotor.

The inner wall of the stator is provided with a plurality of grooves or flutes and in one embodiment of the present invention these are positioned equidistant from each other around the inside wall. In a plan view of the stator having a circular cross-section the grooves may extend radially. Alternatively the grooves may be positioned helically around the inner wall of the stator.

The combination of rotor and stator which is provided by the present invention is suitable for incorporation into mixing apparatus and in particular into mixing apparatus having an upright rotatable shaft.

In this specification the term mixed materials" will be understood to include disintegrated and emulsified materials, the term mixing action to include disintegration and emulsification action and the term materials to be mixed to include materials to be disintegrated and materials to be emulsified and the term mixed to include disintegrated and emulsified.

In a vertical shaft mixer a vertical shaft is provided at its upper end with means for rotation thereof and the vertical shaft extends through a mixing chamber wherein liquids and solids are mixed, disintegrated or emulsified by rotation of the shaft. The device of the present invention may be incorporated by securing the rotor to the lower end of the vertical shaft so that it can rotate with the vertical shaft. The stator generally secured to the floor of the mixingchamber.

The device of the present invention may be incorporated into a change-pan mixer of the type which can be lowered into a mixing chamber and after mixing can be raised. In this case the rotor is secured to the lower end of an upright rotatable shaft driven from above by a motor. The stator is secured to the lower end of the mixing apparatus.

The device may also be incorporated into an in-line continuous mixing apparatus.

When the device is in operation the rotor is rotated within the stator. Materials to be mixed, which may be solids and liquids, or two or more liquids are introduced into the vicinity of the rotor and stator and these materials are drawn between the rotor and the inner wall of the stator by the centrifugal action of the rotor. In general the materials flow in an outwardly flaring, ascending, spiral motion. The materials passing between the stator and the depressions and guide faces on the rotor are disintegrated or emulsified or dispersed by the action of the rotor blades and the stator grooves. When the apparatus is used as a disintegrator and the solids are sheared between the cutting edges of the blades on the rotor and the edges of the grooves or flutes on the stator. The provision of guide faces adjacent to the blades enables the materials to follow preferential flow paths by positioning the solids in the vicinity of the grooves and blades which shear the solid matter. Thus particle size reductions can be achieved. The solid matter is retained within the stator; rotor mechanism for the unexpired portion of the tapering spiral ascent and is subjected to further shearing during their passage.

It has been found that by the provision of preferential paths for materials, between the guide faces and the inner wall of the stator the efficiency of disintegrating, emulsifying and dispersing processes is increased by confining the materials in close proximity to the working members, that is the rotor blades and the stator grooves.

The construction and form of the stator with grooves increase the efficiency of the mechanism by retaining materials within the mechanism for repeated actions by the working members.

The efficiency of the mechanism for disintegrating solids in the presence of liquids may also be due to it operating as a rotating filter which collects and reduces obstructions to a required particle size. Filtration may be achieved by lowering the efficiency of the mechanism as a centrifugal pump and by the provision of restricting members, the latter also functioning as reducers; the methods and operations are further explained as follows.

Liquids and solids below a predetermined size within the mechanism move at lower speeds than the rotor due to the grooves and because the width of the grooves is greater than the thickness of the rotor blades; the liquids and acceptably sized solids are free to pass between apertures formed by the outer faces of the rotor blades and the grooves. The oversize solids are carried at the speed of the rotor by the leading face of the rotor blades and sheared by the cutting edges of the blades and the trailing edges of grooves on the stator.

The fine production of solids is further aided by a grinding action provided by the outer faces of the rotor blades and the inside wall of the stator between the grooves, the clearances between these grinding faces can be varied by vertical adjustments to the shaft or base of mixing apparatus to which the rotor and stator are secured respectively. These vertical adjustments only apply if the stator-rotor configuration is that of a truncated cone or a cylinder with a slight taper. If the configuration is truley cylindrical variations in the clearances between the grinding faces cannot be made in this manner.

When used as an emulsifier or disperser the provision of preferential paths leading to the blades and the grooves may result in efficient and rapid processing because the materials are continuously forced through the apertures formed by the outer faces of the rotor blades and the inner faces of the stator grooves, the width of the grooves being greater than the thickness of the blades.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to particular examples and with reference to the accompanying drawings, wherein:

FIG. 1 is a plan view of one example of the device,

FIG. 2 is a section on line 2-2 of FIG. 1,

FIG. 3 is a plan view of another example of the device,

FIG. 4 is a section on line 44 of FIG. 3,

FIG. 5 is a plan view of another example of the device,

FIG. 6 is a section on line 6-6 of FIG. 5,

FIG. 7 is a view from below of another example of the device,

FIG. 8 is a section on line 8-8 of FIG. 7,

FIG. 9 is a plan view of the device having a rotor of substantially cylindrical form,

FIG. 10 is a section on line l0-l0 of FIG. 9,

FIG. 11 is a vertical section through a batch mixing machine which has the device shown in FIGS. 1 and 2 incorporated therein,

FIG. 12 is a plan view of the machine shown in FIG. 11,

FIG. 13 is a vertical section through a change-pan mixer suitable for the incorporation therein of any one of the devices shown in FIGS. I to 10,

FIG. 14 is a section on line l4l4 of FIGS. 13,

FIG. 15 is a part-sectional view of a continuous mixing apparatus having incorporated therein a device as shown in FIGS. 9 and 10, and

FIG. 16 is a view and section on line l6l6 of FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows one embodiment of a device according to the present invention in plan view and FIG. 2 is a section on line 2-2 of FIG. I. In these figures a rotor l is of an inverted truncated cond configuration and is secured at its upper end to an upright rotatable shaft 4 which can be caused to rotate by means not shown. The rotor I has a number of blades 2 secured thereto by screws 3. Several blades 2 are not shown in the figures. The blades 2 are located substantially axially along the slanting edge of the cone-shaped rotor 1. Between each pair of adjacent blades 2 a depression 5 is formed which leads outwardly to a guide face 6. In the direction of rotation indicated by the arrow F the guide faces 6 precede blades 2. A funnel-shaped stator 7 encloses the rotor l and has an inner wall 8 which is shaped to conform with the outer faces or rotor blades 2. The inner wall 8 of stator 7 has a number of equally spaced grooves 9, the width of grooves 9 being greater than the thickness of rotor blades 2. In plan view grooves 9, rotor blades 2, depressions 5 and guide faces 6 radiate from the axis of the machine. This axis is the vertical axis of rotation passing through the centre of the upright rotatable shaft 4.

The upright rotatable shaft 4 to which the rotor 1 is secured runs at its lower end in a bearing 10 seated in a bearing housing 11 which is secured to the base 12 of the mixing apparatus, the upper part of which is not shown. The stator 7 is mounted on four pillars 13 which are secured to base 12. The rotor 1 has an internal cavity 14 at its lower end which provides a volume of air to be trapped around and over the bearing 10. The volume of air acts as a protective barrier against the entry of undesirable materials into the bearing. (This feature of an air-protected bearing is described in British Pat. specification No. 1,243,227). In operation the rotor 1 is rotated in clockwise direction (FIG. 1) by a motor mounted above (not shown) and coupled to the shaft 4. Alternatively the shaft 4 may be driven through gearing or by roller chains from a prime mover.

A variation of the device is shown in plan view in FIG. 3. FIG. 4 is a section on line 4-4 of FIG. 3. The structure of the stator 7 and the rotor 1 corresponds to that of the device shown in FIGS. 1 and 2, however, the blades 2 are positioned helically on the rotor. The grooves 9 on the stator 7 are positioned helically around the inner wall 8. Helically positioning grooves 9 enables a different flow rate to be achieved when the direction of rotation of rotor 1 is reversed. The flow rate is positive in the clockwise direction in FIG. 3.

A further variation of the device is shown in plan view in FIG. 5. FIG. 6 is a section on line 6-6 of FIG. 5. In this variation a rotor 1 has helically positioned blades 2 secured in position on rotor l by clamps 16 and screws 3. The blades 2 are tapered outwardly on the side adjacent clamps l6 and clamps 16 are reversely tapered at the side adjacent the blade. Between each pair of adjacent blades 2, a depression 5 is formed and this leads outwardly to guide faces 6 and the outer faces of clamps 16 which also serve as guide faces. The blades 2, depressions 5, guide faces 6 and clamps 16 are located helically on rotor 1. Rotor 1 is located within a funnel-shaped stator 7 of the same design as that shown in FIG. 1.

In the embodiment shown in FIGS. 5 and 6 an upright rotatable shaft 4 protrudes from the lower part of rotor 1 and passes through base 12 to which stator 7 is secured by means of four pillars 13. The shaft 4 is rotated from below by means not shown.

The helical positioning of the blades 2, depressions 5, guide faces 6 and clamps 16 on rotor 1 enables the flow rate of materials to be mixed between the rotor and stator to be altered by reversing the direction of rotation of shaft 4 and hence rotor 1. In the clockwise direction of rotation in FIG. 5 the flow rates are positive and the flow rate of the materials being mixed is greater than would be achieved by a perpendicular positioning of the blades 2, depressions 5, guide faces 6 and clamps 16. In the anticlockwise direction of rotation the flow rates are negative and result in a lower pumping or flow rate of the materials being mixed. If the stator is formed with helically positioned grooves as shown in FIGS. 3 and 4 the difference between the two flow rates can be increased.

A further embodiment of the device is shown in FIGS. 7 and 8. In this embodiment rotor l is provided with blades 2, depressions 5, guide faces 6 and 17, and,

clamps 16 which secure blades 2 to the rotor l by means of screws 3. In this embodiment the aforementioned features on the rotor l are not positioned helically but radiate from the axis of the device when viewed from below. Adjacent to each guide face 6 the face of the depression 5 is tapered, the width of the face being least at the lower ends of the blades 2. Adjacent to each clamp 16, a parallel guide face 17 is provided. In this embodiment stator 7 has grooves 9 which are of a different configuration from those shown in FIGS. 1 to 6. The configuration of grooves 9 in FIG. 7 are suitable when solids or a refractory nature are included within the materials to be mixed. The provision of tapered faces of the depression 5 enables the device to accept large solid materials when the rotor l is rotated in the anticlockwise direction in FIG. 7. The large solid material is progressively reduced in size to fine particles during its ascending spiral passage when the device is in operation.

FIGS. 9 and 10 show another embodiment of the device in which the rotor l is of a generally cylindrical shape although a small degree of taper may be incorporated in order that vertical adjustments could be made for working face clearances and to compensate for wear. The rotor l is provided with helically positioned blades 2, and guide faces 6 and 17. In this embodiment the flow rates are unaffected by a reversal of the direction of rotation but parallel and tapered guide faces can be incorporated in the same manner as in FIG. 7. In the clockwise direction of rotation the flow will be an ascending spiral and this direction would normally be used for dealing with large or heavy solids, with a tapered preferential guide path. In the reverse direction the flow will follow a descending spiral motion. In either direction the pitch of the spiral motion is determined by the helix angle of the rotor blades 2.

FIG. 11 is a vertical section through part of a batch mixing machine which has the device shown in FIG. 1 and 2 incorporated therein. An upright rotatable'shaft 4 is driven by a motor (not shown) mounted above the mixing chamber 18. Rotor 1 is secured to the lower end 19 of rotatable shaft 4 by means of screws 20. The air chamber 14 formed by the lower portion of rotor 1 encloses the bearing 10 for shaft 4.

The mixing chamber 18 can be provided with an internal or external heating or cooling jacket. The devices shown in FIGS. 2 to 10 can be similarly incorporated and other types of bearings can be used, for example glanded bearings or shaft seals. 1

FIGS. 13 and 14 show a change-pan mixer into which the devices shown in FIGS. 1 to 10 can be incorporated or any other variation of the device according to the present invention. The rotor l and stator 7 of the device are mounted below plate 22 which is shaped to allow materials to pass through the device. Rotor l is secured to the lower end of rotatable shaft 4 which runs in glanded bearing 21 at the lower end of shaft 4. At its.

upper end shaft 4 runs in a bearing assembly 25 which is carried by a plate 26 to which the motor 24 is se-- cured. If an air-protected lower bearing is to be used in this apparatus, a lower bearing housing would be mounted on a further plate secured to the device by extending the supporting rods and spacer bushes 23 and the lower portion of rotor 1 would be suitably shaped to form an air chamber. In operation the mixer shown in FIGS. 13 and 14 is lowered into a mixing chamber, not shown, and raised after the mixing operation is completed.

FIG. 15 is a part-sectioned view of a continuous mixing apparatus having incorporated therein a device as shown in FIG. 9 and 10. Rotor l is provided with blades 2 and is substantially cylindrical in form. Rotor 1 is located coaxially within stator 7 which is of tubular form and is provided with grooves 9 and in its inner wall surface. Blades 2 are secured to the rotor l.by means of clamps l6 and screw 3. Guide faces 6 are also provided and clamps 16 themselves act as guide faces. The blades 2, guide faces 6, depressions and clamps 16 are positioned helically on the rotor. An air-protected lower bearing 10 is provided at the lower end of shaft 4 as also shown in FIG. 10. Rotor 1 is secured to upright, rotatable shaft 4. The lower bearing housing 11 and lower bearing 10 for shaft 4 are mounted inside a lower chamber 27 which is provided with an inlet indicated by arrow B. Stator 7 is secured to the wall of the lower chamber 28 and to an upper mounting 29. An outlet indicated by the arrow C is formed in upper mounting 29, which carries a motor 24. The upper bearing is also secured to the upper mounting 29.

In operation, materials are introduced into the statorrotor mechanism via a pipe connected to inlet B. The materials ascend spirally through the mechanism for mixing as described earlier. To ensure mixing to the required standards, the mechanism would be of suitable length and the helix angle of the rotor blades selected to provide a suitable pitch for the spiral passage of materials. After mixing, the materials are expelled through outlet C into a pipe connected to the upper mounting 29. A number of machines of the above type may be installed in series in parallel or in an arrangement of both in series and in parallel to suit manufacturing requirements, the complexities of compound formulae, etc.

It has been found that when a device according to the present invention is used for coarse rates of particle size reduction in a disintegration process the depths of the stator grooves are found not to be a determining factor in the control of the particle size. For this function the particle size can be determined by the dimension between the rotor guide faces and the inner wall of the stator. Simple vertical adjustments can be made to the rotor and/or the stator, if the stator-rotor configuration is of a truncated cone shape or a slightly tapered cylindrical configuration, to alter working face clearances to suit product requirements and to compensate for machine wear.

The helical positioning of the rotor blades, depressions, clamps and guide faces can achieve two flow rates of materials to be mixed through the mixing apparatus thereby increasing the versatility of such apparatus and avoiding the higher costs of achieving two flow rates by two speed motors or by twin ratio gear boxes.

The present invention also enables compounds containing heat sensitive materials to be manufactured in one machine and in one continuous operation without interrupting the mixing process for cooling, by the provision for fast and slow flow rates obtained by reversing the direction of rotation of the rotor.

Mixing apparatus incorporating the device of the present invention may be used for mixing various materials, including materials for the production of adhesives and materials for the production of compounds employed as protective coatings, such as powdered mineral pigments and a liquid petroleum medium, the former being dispersed in the latter, or the dispersion of rubber and resins in the manufacture of adhesive compositions. Such mixing apparatus is also useful for the grinding and dispersion of pigments and resins during printing ink and paint manufacture.

I claim:

1. A mixing device for use in mixing apparatuus, said devices comprising a rotor and a stator, said rotor being rotatable about its longitudinal axis and having at least one blade secured thereto, said blade being substantially axially disposed along the rotor and radially extending from the rotor,

said rotor having a guide face adjacent said blade,

said guide face being spaced from the working edge of the blade in a radially inward direction, for guiding the flow of the materials to be mixed in close proximity to the blade towards the cutting edge of the blade such that, when the rotor is rotated, the guide face is upstream of the blade,

said rotor further having a depression disposed substantially axially along the rotor adjacent the guide face,

at least part of said rotor bearing said blade being located within said stator and being substantially coaxial therewith,

said stator having an inner wall which has a plurality of grooves, the width of the grooves being greater than the thickness of the blades.

2. A mixing device according to claim I wherein the rotor has a plurality of blades secured thereto.

3. A mixing device according to claim 2 wherein said rotor has the form of an inverted truncated cone and is located within said stator which has a funnel-shaped configuration.

4. A mixing device according to claim 2 wherein said rotor has the form of a slightly tapering cylinder and said stator is in the form of a hollow cylinder in order to accomodate said rotor.

5. A mixing device according to claim 2 wherein said blades secured to said rotor follow a helical path around said rotor.

6. A mixing device according to claim I wherein said grooves extend helically around said inner wall of said stator.

7. A mixing device according to claim 2 wherein said guide face and said blades have widths substantially uniform along their lengths.

8. A mixing device according to claim 2 wherein said guide faces and said blades have widths varying along their lengths.

9. A mixing device according to claim 1 wherein the direction of rotation of said rotor is reversible.

10. A mixing apparatus for mixing, emulsifying, or disintegrating materials, wherein the improvement comprises a rotor and a stator, said rotor being rotatable about its longitudinal axis and having at least one blade secured thereto, said blade being substantially axially disposed along the rotor and radially extending from the rotor,

said rotor havinga guide face adjacent said blade,

said guide face being spaced from the working edge face,

at least part of said rotor bearing said blade being located within said stator and being substantially coaxial therewith, said stator having an inner wall which has a plurality of grooves, the width of the grooves being greater than the thickness of the blades. 

1. A mixing device for use in mixing apparatuus, said devices comprising a rotor and a stator, said rotor being rotatable about its longitudinal axis and having at least one blade secured thereto, said blade being substantially axially disposed along the rotor and radially extending from the rotor, said rotor having a guide face adjacent said blade, said guide face being spaced from the working edge of the blade in a radially inward direction, for guiding the flow of the materials to be mixed in close proximity to the blade towards the cutting edge of the blade such that, when the rotor is rotated, the guide face is upstream of the blade, said rotor further having a depression disposed substantially axially along the rotor adjacent the guide face, at least part of said rotor bearing said blade being located within said stator and being substantially coaxial therewith, said stator having an inner wall which has a plurality of grooves, the width of the grooves being greater than the thickness of the blades.
 2. A mixing device according to claim 1 wherein the rotor has a plurality of blades secured thereto.
 3. A mixing device according to claim 2 wherein said rotor has the form of an inverted truncated cone and is located within said stator which has a funnel-shaped configuration.
 4. A mixing device according to claim 2 wherein said rotor has the form of a slightly tapering cylinder and said stator is in the form of a hollow cylinder in order to accomodate said rotor.
 5. A mixing device according to claim 2 wherein said blades secured to said rotor follow a helical path around said rotor.
 6. A mixing device according to claim 1 wherein said grooves extend helically around said inner wall of said stator.
 7. A mixing device according to claim 2 wherein said guide face and said blades have widths substantially uniform along their lengths.
 8. A mixing device according to claim 2 wherein said guide faces and said blades have widths varying along their lengths.
 9. A mixing device according to claim 1 wherein the direction of rotation of said rotor is reversible.
 10. A mixing apparatus for Mixing, emulsifying, or disintegrating materials, wherein the improvement comprises a rotor and a stator, said rotor being rotatable about its longitudinal axis and having at least one blade secured thereto, said blade being substantially axially disposed along the rotor and radially extending from the rotor, said rotor having a guide face adjacent said blade, said guide face being spaced from the working edge of the blade in a radially inward direction, for guiding the flow of the materials to be mixed in close proximity to the blade towards the cutting edge of the blade such that, when the rotor is rotated, the guide face is upstream of the blade, said rotor further having a depression disposed substantially axially along the rotor adjacent the guide face, at least part of said rotor bearing said blade being located within said stator and being substantially coaxial therewith, said stator having an inner wall which has a plurality of grooves, the width of the grooves being greater than the thickness of the blades. 